EDIT: Oh, it's a Google Groups response:

  We're writing to let you know that the group you tried to contact (careers) may not exist, or you may not have permission to post messages to the group. A few more details on why you weren't able to post:

  * You might have spelled or formatted the group name incorrectly.
  * The owner of the group may have removed this group.
  * You may need to join the group before receiving permission to post.
  * This group may not be open to posting.